Claustroneocortical projections studied in the cat by means of multiple retrograde fluorescent tracing.

The topographical interrelations of claustroneocortical cells and their degree of divergent collateralization were investigated in cat by means of retrograde fluorescent double labeling. The tracers Fast Blue (FB) and Nuclear Yellow (NY) were injected in several combinations in two different cortical fields. FB-labeled and NY-labeled cells were found in all cases in the insular portion of the ipsilateral claustrum (CII). The distributions of labeled cells confirmed the organization reported in previous studies. In some cases the two labeled cell populations were segregated in different parts of the CII; in other cases there was more or less overlap in the two distributions. The degree of overlap was not simply related to the topographic proximity of the injected cortical territories. In all cases the vast majority of cells were single labeled. In one case both FB and NY were injected in the same cortical area in order to control that claustral axons can retrogradely transport two tracers back to the same parent cell bodies. In this control case CII cells were double labeled. All together these data indicate that widely divergent claustroneocortical projection take origin mainly from separate cells.